As part of WLE's partnership with The Economist's Sustainability Summit this March in London, the Thrive blog is publishing a series of posts that discuss the role science plays in catalyzing shifts toward sustainability in the private sector and beyond. This blog explores the resilience of urban food systems in light of a changing climate and was originally published on Zilient.org.

Pozo counts money he has received from working as a farm-hand on an urban plot in Ghana.

Getting food from farms to urban centers raises a number of well-known issues: transporting fresh food can be costly and complicated, leading to concerns about affordability, nutritional quality and environmental impact.

But with the advance of climate change, yet another question is quickly rising to the top of the list: how can cities secure a reliable supply of food when droughts, floods and other extreme weather events are frequently interrupting supply chains?

Go local - or go global?

The local food movement has increasingly been touted as a solution for a reliable, affordable supply of food to cities, especially in the developed world.

Concepts such as “vertical farming” – growing food in skyscrapers using hydroponics to bypass the need for soil or sunlight – has generated a great deal of interest, and it will likely be one of a diverse set of urban agriculture types we will see more of in the future.

Urban agriculture already plays a greater role in global food production than what we might think, with 456 million hectares—an area nearly half the size of the USA—under cultivation within 20km of the world’s cities, and 67 million hectares being farmed in open spaces in the urban core.

Yet, the findings of a recent study imply relying on urban farming is not enough.

In fact, we have found there is little evidence that local food systems are inherently better than national or global ones when it comes to securing supplies. Rather, a diversified urban food supply system, with food originating from a range of sources, might instead bolster a city’s resilience because it would be less sensitive to the impacts of climate change. In this scenario, even if farms near a city are flooded and the harvest lost, food from other sources might still be available.

For example, vegetable supplies in Spain were recently affected by extreme weather after lots of rain and then lots of snow in the Mediterranean. Subsequent shortages of aubergine, courgette and lettuces forced prices up, affecting the domestic market as well as the international market.

Considering the risks of such a dependence on a singular food source, what can we say about the resilience of some of world’s fastest growing cities?

The tale of two West African cities

Ouagadougou, the capital of Burkina Faso, experienced a 400 percent population increase between 1985 and 2012, swelling to almost 2 million people today. In Tamale, in neighboring Ghana, the urban population has doubled every decade since 1970, today reaching about 400,000.

The results showed that both cities relied heavily on agricultural production in nearby areas to meet urban food demand. About a third of the food supplying Tamale originated from within 30km and half from within 100km. Some foods came almost solely from within the city itself; 90 per cent of leafy vegetables, which are an important part of traditional diets and rich in nutrients, were supplied by urban farming.

But both cities also depended on supplies of some food from further afield. For example, Ouagadougou is heavily reliant on imported rice, an important staple food that cannot easily be substituted by other crops. While it is grown in the region, domestic production cannot meet the demand.

At the same time, we also saw that climate change-induced weather events can have grave consequences for urban food supply: in 2007, droughts and subsequent floods in northern Ghana destroyed half of all staple crops. The results were, again, food shortages and rising prices.

Investing in diverse supply chains

The findings of the Ouagadougou-Tamale study imply that achieving a sustainable, resilient urban food system is not a simple question of either local or global food supply chains; both are necessary. The more diverse urban food supply systems are, the more resilient.

Local agricultural production needs to be considered in urban planning because most cities already are dependent on locally produced food. Overall, the extent of urban agriculture on a global scale warrants a reorientation of agricultural policies and development work, which are mostly focused on rural contexts.

Further, locally produced food comes with a set of significant advantages: the carbon footprint is lower, and food reaches consumers when it is fresh. Not least, local production safeguards the livelihoods and incomes of smallholders.

Yet it cannot stand alone; relying on a single cluster of high-rise buildings or peri-urban farms to provide a megacity with all the food it needs is just too risky.

Instead, planning for resilient food systems in cities of the future will require a holistic perspective. Focusing on diversity – including diverse sources, actors, means of transportation and more – may be the first step toward reliably securing food for growing urban populations in the face of climate change.

As we head for a world with many more mouths to feed, variety may be more than just the spice of life – it may be its bread and butter too.

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